The introduction of fibers and other fillers into a polymeric matrix is an established route to enhancing the physical properties of a chosen polymer provided good dispersion and intimate interfacial adhesion can be achieved. This method can also be very cost effective providing the filling agents are obtainable at low to moderate cost.
Previous studies have shown successful improvements in mechanical properties of polymers by the formation of microcomposites through purely physical mixing of fiber fillers into the polymer. For example, Oksman et al. (Oksman, K., M. Skrifvars, and J. F. Selin, Natural fibres as reinforcement in polylactic acid (PLA) composites. Composites Science and Technology, 63(9):1317-1324, 2003) embedded flax fibers into a polylactic acid (PLA) matrix and compared the resulting composite properties to polypropylene (PP) filled with the same fibers. It was found that the mechanical properties of the flax-PLA composites are promising, since the composite strength was about 50% better compared to similar flax-PP composites that are used in many industrial applications. However, microscopy studies suggested a lack of interfacial adhesion between the polymer matrix and the fiber surface. Additionally, Huda et al. (Huda, M. S., et al., Effect of processing conditions on the physico-mechanical properties of cellulose fiber reinforced poly(lactic acid). ANTEC 2004 Plastics: Annual Technical Conference, Volume 2: Materials, 2:1614-1618, 2004; Huda, M. S., et al. Physico-mechanical properties of “Green” Composites from poly(lactic acid) and cellulose fibers, at GPEC, Detroit, USA, 2004) showed improvement of the tensile strength, tensile modulus and impact strength upon reinforcing PLA with cellulose fibers. However, the introduction of cellulose fibers did not affect the glass transition temperature significantly as measured by DSC.
Thus, there is a desire for improved polymer composites but there exits a need for an improved method of making these filled polymers to achieve the desired polymer physical characteristics rapidly and at an acceptable cost.